[CS] Paper 2/1-Data Representation/1.6 Compression & Encryption

Created by: 16tgc05
Created on: 17-10-21 10:57

What is the difference between 'lossy compression' and 'Lossless compression' ?

Lossy compression physically removes data from the source file which means it can't be fully
rebuilt into it original form.
Lossless compression looks for patterns and
stores the data in a different way based on the patters.
It means that a file can be

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What is RLE (Run-length encoding) ?

Where runs of data are stored as data values and counts rather than runs.
For example rather than storing 'WWWWBBB'
'4W3B' would be stored

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What is 'dictionary based compression' ?

Words/characters in the file are added to a dictionary. Rather than storing the binary
for each character, the index in the dictionary is
stored and referenced instead.

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How does 'Caesar cipher' work ?

A new alphabet is created by shifting the
standard one forwards or backwards a given number of times

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How does 'Vernam cipher' work ?

Instead of a single key, each character is encrypted using its own key. The key (one-time pad) is randomly generated and its length must be equal to the plaintext. Both character are converted to binary (ASCII) and the XOR is used to decide 1 or 0.

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Other cards in this set

Card 2

Front

What is RLE (Run-length encoding) ?

Back

Where runs of data are stored as data values and counts rather than runs.
For example rather than storing 'WWWWBBB'
'4W3B' would be stored

Card 3

Front

What is 'dictionary based compression' ?

Back

Card 4

Front

How does 'Caesar cipher' work ?

Back

Card 5

Front

How does 'Vernam cipher' work ?

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[CS] Paper 2/1-Data Representation/1.6 Compression & Encryption